Description of Prior Art
In the past, railway vehicles, planes, trucks, buses and other mechanisms have been stopped by several kinds of brakes.
In 1827 John B. Jervis invented and installed on a train a large windmill like mechanism geared to the axles which held a train brake when descending mountain grades.
From the time that the first train began to roll until 1868 various mechanisms were used to brake trains, none of which were effective.
In 1868 the first Westinghouse brake was devised in which a steam-actuated pump on a locomotive rammed compressed air into a large reservoir. When a valve in the cab was opened, part of the supply rushed back through pipes and hoses to a cylinder under each car driving a piston connected by rods and levers to the brakes, causing their "shoes" to press against the tires on the wheels.
However, this "straight air brake" had three faults; first if there was a rupture in the system it would not work at all, second when cars became uncoupled on upgrades, only manual braking could keep them from rolling backward and finally, compressed air was slow in reaching the rear cylnders of a long train.
Westinghouse solved two of these problems in 1871, when an "automatic air brake" was brought out which failed safe. The pump and main reservoir were unchanged, but each car carried a small auxiliary tank and a mechanism called a "triple valve" which opened and closed passages by allowing one pressure to overcome another.
Under normal running conditions all of the reservoirs, together with the pipes and hoses, which collectively formed a continuous system called the train line, were fully charged, by the triple valves kept air out of the brake cylinders. For decelerations and full stops the engineer opened the control valve in the cab, letting some of the air in the train line escape to the atmosphere. The triple valve responded to lessened pressure by permitting the more highly compressed air in the small tanks to flow to the brake cylinders, where it exerted a force equal to the reduction in the line. The brakes were released by closing the main valve again, giving the pump a chance to recharge the system while at the same time the triple valves shut off the passages to the cylinders and voided the air within them.
Smooth braking was insured by providing graduated escape ports in the control valve, each hole allowing a 15 percent reduction. Only in emergencies was the handle swept with a single motion through its arc, uncovering all of the openings at once. This drastic action was variously known as "dynamiting her," "dumping the air," or "big-holding the Westinghouse." A parted or blown-out hose produced the same effect, applying the full force to the wheels.
Other braking systems used at this time were the so-called "independent systems" which used momentum as a decelerating force. All of their arrangements called for engines fitted with steam brakes. When the locomotives slowed down, the cars behind them bunched together, compressing spring-loaded buffers at their ends. In turn, the buffers shoved on levers which actuated the train brakes.
Another brake manufacturer was the Eames Vacuum Brake Company of Boston. In its system a steam-operated "ejector" took the place of a pump and drew air out of a bowl-shaped vessel under each car when a control valve was opened. This caused an India-rubber cover to be driven inward by the greater atmospheric pressure on its outer face, and the motion of the diaphragm was transmitted by rods and cams to the brakes. Westinghouse went on to modify his automatic system in a manner which permitted air to be voided to the atmosphere not only through the engineer's control valve but at every triple valve.
The Westinghouse and all other brakes rely on mechanical friction to turn the kinetic energy into heat and thus stop the vehicle or mechanism. All of these brakes involve a brake shoe or friction pads being applied directly to the wheel, brake drum or disc.
Other pertinent brakes which are known in the art are shown in the French patent of Legrande No. 543,694 which discloses a reciprocating fluid damper brake driven by a wheel and having linkage connected to an off center driving pin and U.S. Pat. No. 3,200,906 which discloses a plurality of hydraulic jacks which push a long pressure plate against two flexible strips and four friction plates to provide a plane brake.
With the present energy shortage there is a great need for high speed ground transportation as an attractive alternate to using the already badly overcrowded air-ways, and to induce more people to leave their energy extravagant private vehicles at home. Rather than the 100 MPH speed allowed by present brakes 200-300 MPH trains are now needed.
Besides high-speed passenger service there is a great need to increase the speed of freight trains. The closer the speed of freight trains approaches that of the fastest passenger trains the better, for the more intensively tracks are used, the more economical they are. The faster the speed and the closer to a uniform speed the trains can get, the more journeys each train can make and the more trains can run over one pair of rails. At present all freight trains must significantly decrease speed on downgrades because of the hazard of overheating brakes. If trains can obtain a higher speed, fewer trains and fewer tracks can do more work and reduce capital cost.
At present there is no brake which will completely stop a high speed vehicle and prevent the danger of brake fade. There have been many attempts to invent a successful retarder brake but results have been limited in many respects.
The British new Advanced Passenger Train has four powered axles which use dynamic brakes and six non-powered axles which are fitted with a retarder brake which churns a water-glycol solution and imparts some of the kinetic energy to the water. This system is ineffective at low speed and the train relies on friction brakes to stop it so only 7% of the total braking energy is absorbed by the hydro-kinetic retarder.
Other plans for high speed trains call for electric powered trains with small motors spread along the train adapted to use regenerative or rheostatic braking by reversing the polarity of the motors and thus absorbing the energy of braking. This type of braking is impractical in a country which has large distances to cover such as the U.S.A., Canada, Australia, and most of the areas of the world. The many miles of electric line or third rail and the many power substations which are required make this system economically impractical.
Tentative plans in the U.S. call for high speed rail systems, the most promising of which is the Tracted Air Cushion Vehicle which will travel at speeds of up to 250 MPH. This system will have landing gear with wheels to be braked in order to stop the vehicle. According to the latest report to Congress and the President on the High Speed Transportation Act of 1965, there is not yet a single brake which will take a high speed vehicle from top speed to full stop.
In addition to train brakes other transportation vehicles suffer from brake failure. For example airplane brakes will fail if the reverse thrust of the plane fails to operate. The usual result of this failure is for the plane to run off the runway with the tires burning off, increasing the possibility of the hydraulic fluid catching fire. Large trucks and buses operating in hilly or mountainous terrain often have brake failure from overheating brakes resulting in many lives lost each year.
The present invention generally relates to a friction disc brake which looks much like a conventional disc brake but has the advantage that it also operates in a second mode in which the torque load is shared by a fluid brake mode or the torque load is assumed completely by the fluid brake mode thus relieving the friction mode of any share of the load. This is accomplished by supplying the friction disc with a tilting mechanism and by providing a by-pass hydraulic conduit to allow the hydraulic fluid to circulate from the brake cylinders on one side of the disc past the master cylinder through a cooling circuit, through the opposite brake cylinders and then back to the first cylinder as it is pumped by the reciprocating disc and pistons. A shut-off valve is provided to increase the pressure and to complete the braking in the second mode. Cooling fins or a radiator are utilized to dispel the heat from the friction brake mode and the fluid brake mode.
An alternate brake embodiment relates to a frictionless fluid brake in which braking is accomplished by tilting the disc which converts the rotary motion to reciprocal with the result that the brake cylinders reciprocatively pump the fluid in a circuit through a shut-off valve and a radiator or cooling fins.
In the invention kinetic energy is converted into heat by the shearing of the fluid and the heat is dispelled through the radiator. To completely stop the rotating member from rotating, the shut-off valve is closed completely.
A third cool running brake system can be constructed by circulating the hydraulic fluid of a conventional disc brake through a cooling system. A low efficiency pump such as a centrifugal pump carries the hydraulic fluid through a line which by-passes the master cylinder and pumps it through cooling fins or a radiator while the brakes are in use. The pump can be linked to the rotating member or powered by any type of motor.
The present invention can be easily adapted to be placed on presently operable automobiles, trunks, trains, airplanes, tracted air cushion vehicles and other diverse mechanisms. With the invention's simple sturdy construction, it can be inexpensively adapted to any desired usage. The invention cuts maintenance costs because brake shoe and wheel wear is drastically reduced and gives a quick even stop without lock-up.
The invention is particularly useful in that it provides a safe, dependable brake which is cooler and which will completely eliminate the hazards of brake fade which currently exist with all present commercial brakes.
In the invention, heat is reduced and removed to an area remote to the wheels and tires and is expelled through a radiator.
The benefits that are derived from the use of such novel brakes are that the brake would be the only brake needed at any speed with little or no wear on the wheels or brake blocks of trains. The brake is unaffected by water or the elements, is fail safe, would be safe in an explosive atmosphere and can be remotely controlled by pneumatic, hydraulic, solenoid, or cable means.